VPNs can slow down internet speed by 10-20%

VPNs can slow down internet speed by around 10-20% due to factors like routing traffic to a VPN server, server distance impacting speed, and encryption processes. Issues like server distance, encryption overhead, tunneling protocol, VPN server infrastructure, and using a free VPN can contribute to slower speeds. Mitigation strategies include choosing a server near your location, running speed tests, opting for lightweight VPN protocols like WireGuard, and selecting a reliable VPN provider with fast speeds like NordVPN, ExpressVPN, or CyberGhost VPN

While VPNs may slightly decrease speed, the added security and privacy benefits generally outweigh the minor slowdowns for most users.
https://www.techrepublic.com/article/does-vpn-slow-down-internet-speed/